It is known to fabricate pulleys out of stamped complementary half sections which are fastened together, as by welding. The hub portions of such pulleys typically have keys which interlock with a shaft to transmit torque between the shaft and pulley. However, it is a problem to securely anchor the shaft to the pulley without play therebetween. Various fasteners have been suggested for this purpose, for example, the set screws illustrated in U.S. Pat. Nos. 3,094,009 and 3,324,735. Such set screws have only a small area of frictional contact and do not effectuate an adequately tight and play-free coupling.